As is known in the art, monolithic microwave integrated circuit transceivers have been used in many applications. One such application is in phased array antenna systems. In such system, an antenna beam is formed by providing a proper gain and phase to each one of the antenna elements in the array. In one application, a transceiver MMIC module is coupled to each one of the antenna elements to provide this proper gain and phase shift. Because the antenna is adapted to operate in both a transmit mode and a receive mode, attempts have been made to provide a module where there are common elements adapted for use in both the transmit and receive modes. One such transceiver is described in U.S. Pat. No. 4,635,062 “Transceiver Element for Phased Array Antenna” inventors Berig et al, issued Jan. 6, 1987 assigned to the same assignee as the present invention.
More particularly, the receive (R) circuitry includes low noise amplification (LNA) and phase/amplitude setting circuits. The transmit (T) circuitry includes phase/amplitude setting circuits and power amplification (PA). The circuitry that is in common between is the phase/amplitude setting circuits and in Transmit/Receive (T/R) systems (i.e., transceiver) where T and R have the same frequency, this circuitry can be shared. Therefore, Common-Leg (CL) circuits that include the phase/amplitude setting along with some amplification have been implemented in T/R modules to reduce part count, save space and save cost. This concept in the past has not included the LNA or PA because these functions have been better implemented for optimal performance using separate technologies. Fully integrated T/R CL circuits have been attempted in the past but at the cost of noise figure and/or transmit power of the system. The attempts usually had to trade off performance in receive or transmit due to losses in switching and signal routing that are required to change the antenna connection from T to R.